Halogenated phenols are widely used fungicidal agents. These water-insoluble halogenated phenols can be converted into water-soluble compounds by reaction with an alkaline agent. Although simple in theory, this reaction is connected with numerous problems. For instance, since both the insoluble compounds and the soluble compounds are toxic, strict measures must be taken to avoid environment contamination and worker exposure. Also, drying the soluble product involves complicated safety risks because dusting problems arise and because an additional granulation step often is required to give the dried product a form appropriate for use. Further, the drying step must not involve too high temperatures since this might degrade the product and/or generate still more toxic by-products. This limitation complicates and extends the drying step and reduces cost efficiency.
When the costs of drying and the dangers of handling dusts become too severe, an alternative solution is to package and ship the product without removing the liquid. This is not often an economical solution since containers for liquids usually are more expensive than those for solids and the added weight and volume increases shipping costs.
The above mentioned problems have become so troublesome in recent years that one of the largest manufacturers of sodium pentachlorophenate monohydrate ceased manufacturing operations because of the excessive expense of upgrading both procedures and equipment in order to meet current standards for worker's safety and pollution abatement. This manufacturer's process involved the following reaction: ##STR1##
This reaction was carried out in enough water to dissolve the NaOH and to hold the sodium chlorophenate product in solution. Since the solubility of the sodium pentachlorophenate is somewhat limited in water, the weight of the water that had to be removed at the end of the reaction was in the range of from 3 to 5 times the weight of the solid product. The apparatus conventionally used to remove this water was a fluidized bed dryer, which consumed substantial amounts of energy. A drum drier could have been used instead of a fluidized bed drier but the product of a drum drier are flakes that are subject to considerable dusting. A fluidized bed dryer is objectionable because the higher process temperatures required for efficient operation favor the formation of dioxins, which are notorious for extreme toxicity.